1. Field of the Invention
The present invention relates to recording magnetic heads for use typically in floating magnetic heads. More specifically, it relates to magnetic heads which less adversely affect surrounding constitutional members even when a current at a high frequency and/or a high power is applied.
2. Description of the Related Art
FIGS. 10 and 11 illustrate a conventional magnetic head H100, in which FIG. 10 is a partial plan view when viewed from above (from the Z1 direction in FIG. 10), and FIG. 11 is a sectional view thereof taken along the lines X1-X1 in FIG. 10 when viewed from the X2 direction in FIG. 10.
The magnetic head H100 illustrated in FIGS. 10 and 11 has a write magnetic head H100w which is an “inductive head”. The write magnetic head H100w is arranged over a read magnetic head H100r utilizing, for example, a magnetoresistive effect.
The magnetic head H100 shown in FIGS. 10 and 11 is arranged over a trailing end 101a of a slider 101. The slider 101 contains a ceramic and constitutes a floating head.
The read magnetic head H100r is arranged over the trailing end 101a of the slider 101 with the interposition of an Al2O3 film 102. The read magnetic head H100r detects a magnetic field from a recording medium such as a hard disk utilizing the magnetoresistive effect and thereby reads out recording signals.
The read magnetic head H100r includes a lower shield layer 103, a lower gap layer 104, a magnetic read station M, an upper gap layer 105, and an upper shield layer 106 arranged in this order. The magnetic read station M is arranged partially between the lower gap layer 104 and the upper gap layer 105.
The lower gap layer 104 and the upper gap layer 105 each contain an insulating material such as Al2O3 or SiO2. The lower shield layer 103 and the upper shield layer 106 each contain a soft magnetic material having a high magnetic permeability, such as a NiFe alloy (Permalloy).
A separating layer 107 containing an insulating material such as Al2O3 or SiO2 is arranged over the upper shield layer 106, and the write magnetic head H100w is arranged over the separating layer 107.
A lower core layer 110 is arranged over the separating layer 107. A Gd-deciding layer 111 for deciding a gap depth (Gd) is arranged over the lower core layer 110.
A magnetic pole 112 extends from a side T facing a recording medium to the Gd-deciding layer 111.
The magnetic pole 112 includes a lower magnetic pole layer 113, a non-magnetic gap layer 114, and an upper magnetic pole layer 115 arranged in this order from the bottom. The upper magnetic pole layer 115 is magnetically connected to an upper core layer 116 arranged over the upper magnetic pole layer 115.
The upper magnetic pole layer 115 and the lower magnetic pole layer 113 each contain a soft magnetic material such as a NiFe alloy.
A coil insulating underlayer 117 is arranged over the lower core layer 110 toward the rear of the Gd-deciding layer 111 in a direction of height (the Y direction in FIGS. 10 and 11), and over the coil insulating underlayer 117 is arranged a first coil layer 118a in a helical pattern. The first coil layer 118a is made of an electrically conductive material such as Cu. A second coil layer 118b is arranged over the first coil layer 118a with the interposition of a coil insulating underlayer 123.
The first coil layer 118a and the second coil layer 118b constitute a coil layer 118. An insulating layer 119 is arranged around the first coil layer 118a, and an insulating layer 120 is arranged around the second coil layer 118b. These insulating layers are each made of an organic or inorganic insulating material.
The upper core layer 116 has a rear anchor 116a connected to the top of a connection layer 121. The connection layer 121 is arranged over the lower core layer 110 and is made of a magnetic material.
The upper core layer 116 and the lower core layer 110 are each typically formed from a NiFe alloy by plating.
A protective layer 122 made typically of alumina is arranged over the upper core layer 116.
When a recording current is supplied to the coil layer 118, a recording magnetic field is induced at the lower core layer 110 and the upper core layer 116. A leakage field is formed between the lower magnetic pole layer 113 and the upper magnetic pole layer 115 that face each other via the gap layer 114. Magnetic signals are recorded on a recording medium, such as a hard disk, by the action of the leakage field.
The magnetic head having the above structure is disclosed in Japanese Unexamined Patent Application Publication No. 2003-085710.
The conventional magnetic head H100 having the structure shown in FIGS. 10 and 11 disclosed in the publication undergoes an increasing write frequency and an increasing write current in the write magnetic head H100w with an increasing recording density employed in recent years.
With an increasing write frequency and an increasing power of write current in the write magnetic head H100w, Joule heat caused by such a high frequency and high power is produced in the upper shield layer 106 in the read magnetic head H100r, to thereby expand the upper shield layer 106. This results in stress upon the upper shield layer 106, which causes change in magnetic domains of the upper shield layer 106. Thus, the magnetic permeability of the upper shield layer 106 changes, resulting in stress applied upon the read magnetic head H100r. 
Consequently, the output of the read magnetic head H100r changes between before and after the application of stress.
This phenomenon is called as write induced instability (WII). Recently, a recording magnetic field at a high frequency and/or a high power is applied to the write magnetic head as mentioned above. The magnetic head is therefore used in recording at a higher density, and the magnetic permeability in the upper shield layer 106 changes further more. Consequently, WII significantly affects the reproducing properties (output properties) of the read magnetic head H100r. 
Accordingly, the change in magnetic domains of the upper shield layer 106 must be minimized even when a current at a high frequency and/or a high power is applied to the write magnetic head H100w. 
In particular, the magnetic head H100 is frequently subjected to an acceleration test for determining magnetic properties of a magnetic detecting device 100 upon application of a current at a frequency and/or a power higher than those of a current applied to the write head in practical use. In this case, the read magnetic head H100r suffers from a higher stress, which causes significant changes in magnetic domains and in magnetic permeability of the upper shield layer 106. Thus, WII significantly occurs.
Strong demands have therefore been made to effectively reduce WII and appropriately minimize the change in magnetic domains of the upper shield layer 106 in the acceleration test.
Above-mentioned Japanese Unexamined Patent Application Publication No. 2003-085710, however, does not focus attention on reduction of WII and never teaches how the upper shield layer 106 is configured so as to reduce the change in magnetic domains even when a current at a high frequency and/or a high power is applied to the write magnetic head H100w. 
Consequently, the magnetic head having the structure shown in FIGS. 10 and 11 disclosed in Japanese Unexamined Patent Application Publication No. 2003-085710 can neither reduce WII nor improve reproducing properties (output properties) of the read magnetic head H100r. 